C++ PQcancel函数代码示例

/* MultiClientCancel cancels the running query on the given connection. */
bool
MultiClientCancel(int32 connectionId)
{
	PGconn *connection = NULL;
	PGcancel *cancelObject = NULL;
	int cancelSent = 0;
	bool canceled = true;
	char errorBuffer[STRING_BUFFER_SIZE];

	Assert(connectionId != INVALID_CONNECTION_ID);
	connection = ClientConnectionArray[connectionId];
	Assert(connection != NULL);

	cancelObject = PQgetCancel(connection);

	cancelSent = PQcancel(cancelObject, errorBuffer, sizeof(errorBuffer));
	if (cancelSent == 0)
	{
		ereport(WARNING, (errmsg("could not issue cancel request"),
						  errdetail("Client error: %s", errorBuffer)));

		canceled = false;
	}

	PQfreeCancel(cancelObject);

	return canceled;
}

static void
handle_sigint(SIGNAL_ARGS)
{
	int			save_errno = errno;
	char		errbuf[256];

	/* if we are waiting for input, longjmp out of it */
	if (sigint_interrupt_enabled)
	{
		sigint_interrupt_enabled = false;
		siglongjmp(sigint_interrupt_jmp, 1);
	}

	/* else, set cancel flag to stop any long-running loops */
	cancel_pressed = true;

	/* and send QueryCancel if we are processing a database query */
	if (cancelConn != NULL)
	{
		if (PQcancel(cancelConn, errbuf, sizeof(errbuf)))
			write_stderr("Cancel request sent\n");
		else
		{
			write_stderr("Could not send cancel request: ");
			write_stderr(errbuf);
		}
	}

	errno = save_errno;			/* just in case the write changed it */
}

/*
 * Console control handler for Win32. Note that the control handler will
 * execute on a *different thread* than the main one, so we need to do
 * proper locking around those structures.
 */
static BOOL WINAPI
consoleHandler(DWORD dwCtrlType)
{
	char		errbuf[256];

	if (dwCtrlType == CTRL_C_EVENT ||
		dwCtrlType == CTRL_BREAK_EVENT)
	{
		/* Send QueryCancel if we are processing a database query */
		EnterCriticalSection(&cancelConnLock);
		if (cancelConn != NULL)
		{
			if (PQcancel(cancelConn, errbuf, sizeof(errbuf)))
				fprintf(stderr, _("Cancel request sent\n"));
			else
				fprintf(stderr, _("Could not send cancel request: %s"), errbuf);
		}
		LeaveCriticalSection(&cancelConnLock);

		return TRUE;
	}
	else
		/* Return FALSE for any signals not being handled */
		return FALSE;
}

static PyObject *
psyco_conn_cancel(connectionObject *self, PyObject *args)
{
    char errbuf[256];

    EXC_IF_CONN_CLOSED(self);
    EXC_IF_TPC_PREPARED(self, cancel);

    /* do not allow cancellation while the connection is being built */
    Dprintf("psyco_conn_cancel: cancelling with key %p", self->cancel);
    if (self->status != CONN_STATUS_READY &&
        self->status != CONN_STATUS_BEGIN) {
        PyErr_SetString(OperationalError,
                        "asynchronous connection attempt underway");
        return NULL;
    }

    if (PQcancel(self->cancel, errbuf, sizeof(errbuf)) == 0) {
        Dprintf("psyco_conn_cancel: cancelling failed: %s", errbuf);
        PyErr_SetString(OperationalError, errbuf);
        return NULL;
    }
    Py_INCREF(Py_None);
    return Py_None;
}

static BOOL WINAPI
consoleHandler(DWORD dwCtrlType)
{
	char		errbuf[256];

	if (dwCtrlType == CTRL_C_EVENT ||
		dwCtrlType == CTRL_BREAK_EVENT)
	{
		/*
		 * Can't longjmp here, because we are in wrong thread :-(
		 */

		/* set cancel flag to stop any long-running loops */
		cancel_pressed = true;

		/* and send QueryCancel if we are processing a database query */
		EnterCriticalSection(&cancelConnLock);
		if (cancelConn != NULL)
		{
			if (PQcancel(cancelConn, errbuf, sizeof(errbuf)))
				write_stderr("Cancel request sent\n");
			else
			{
				write_stderr("Could not send cancel request: ");
				write_stderr(errbuf);
			}
		}
		LeaveCriticalSection(&cancelConnLock);

		return TRUE;
	}
	else
		/* Return FALSE for any signals not being handled */
		return FALSE;
}

bool
CancelQuery(PGconn *conn, int timeout)
{
	char errbuf[ERRBUFF_SIZE];
	PGcancel *pgcancel;

	if (wait_connection_availability(conn, timeout) != 1)
		return false;

	pgcancel = PQgetCancel(conn);

	if (pgcancel != NULL)
	{
		/*
		 * PQcancel can only return 0 if socket()/connect()/send()
 		 * fails, in any of those cases we can assume something
		 * bad happened to the connection
		 */
		if (PQcancel(pgcancel, errbuf, ERRBUFF_SIZE) == 0)
		{
			log_warning(_("Can't stop current query: %s\n"), errbuf);
			PQfreeCancel(pgcancel);
			return false;
		}

		PQfreeCancel(pgcancel);
	}

	return true;
}

/*
 * Handle interrupt signals by cancelling the current command.
 */
static void
on_interrupt(void)
{
	pgutConn   *c;
	int			save_errno = errno;

	/* Set interruped flag */
	interrupted = true;

	if (in_cleanup)
		return;

	/* Send QueryCancel if we are processing a database query */
	pgut_conn_lock();
	for (c = pgut_connections; c; c = c->next)
	{
		char		buf[256];

		if (c->cancel != NULL && PQcancel(c->cancel, buf, sizeof(buf)))
			elog(WARNING, "Cancel request sent");
	}
	pgut_conn_unlock();

	errno = save_errno;			/* just in case the write changed it */
}

GSQLCursorState 
pgsql_cursor_stop (GSQLCursor *cursor)
{
	GSQL_TRACE_FUNC;
	
	GSQLSession *session;
	GSQLEPGSQLSession *spec_session;
	GSQLEPGSQLCursor *spec_cursor;
	PGcancel *cancel = NULL;
	gchar buff[256];
	
	g_return_val_if_fail (GSQL_IS_CURSOR (cursor), GSQL_CURSOR_STATE_ERROR);

	session = cursor->session;
	g_return_val_if_fail (GSQL_IS_SESSION (session), 
	                      GSQL_CURSOR_STATE_ERROR);

	spec_session = session->spec;
	spec_cursor = cursor->spec;

	cancel = PQgetCancel (spec_session->pgconn);
	if ( ! PQcancel (cancel, buff, 256) ) {
		pgsql_session_workspace_info (session, buff);
		PQfreeCancel (cancel);
		return GSQL_CURSOR_STATE_ERROR;
	}
	PQfreeCancel (cancel);
	return GSQL_CURSOR_STATE_STOP;
}

void dbgPgConn::Cancel()
{
	// Attempt to cancel any ongoing query
	if (m_pgConn)
	{
		PGcancel *cancel = PQgetCancel(m_pgConn);
		char errbuf[256];
		PQcancel(cancel, errbuf, sizeof(errbuf));
		PQfreeCancel(cancel);
	}
}

static void
CancelQuery(void)
{
	char errbuf[256];
	PGcancel *pgcancel;

	pgcancel = PQgetCancel(primaryConn);

	if (!pgcancel || PQcancel(pgcancel, errbuf, 256) == 0)
		fprintf(stderr, "Can't stop current query: %s", errbuf);

	PQfreeCancel(pgcancel);
}

static void
CancelQuery(void)
{
	char errbuf[ERRBUFF_SIZE];
	PGcancel *pgcancel;

	pgcancel = PQgetCancel(primaryConn);

	if (!pgcancel || PQcancel(pgcancel, errbuf, ERRBUFF_SIZE) == 0)
		log_warning("Can't stop current query: %s\n", errbuf);

	PQfreeCancel(pgcancel);
}

void
CancelQuery(PGconn *conn)
{
	char errbuf[ERRBUFF_SIZE];
	PGcancel *pgcancel;

	pgcancel = PQgetCancel(conn);

	if (!pgcancel || PQcancel(pgcancel, errbuf, ERRBUFF_SIZE) == 0)
		log_warning(_("Can't stop current query: %s\n"), errbuf);

	PQfreeCancel(pgcancel);
}

CAMLprim value PQCancel_stub(value v_conn)
{
  CAMLparam1(v_conn);
  PGconn *conn = get_conn(v_conn);
  if (conn == NULL) CAMLreturn(v_None);
  else {
    PGcancel *cancel = get_cancel_obj(v_conn);
    char errbuf[256];
    int res;
    caml_enter_blocking_section();
      res = PQcancel(cancel, errbuf, 256);
    caml_leave_blocking_section();
    if (res == 0) CAMLreturn(v_None);
    else CAMLreturn(make_some(caml_copy_string(errbuf)));
  }
}

/*
 * Handle interrupt signals by cancelling the current command,
 * if it's being executed through executeMaintenanceCommand(),
 * and thus has a cancelConn set.
 */
static void
handle_sigint(SIGNAL_ARGS)
{
	int			save_errno = errno;
	char		errbuf[256];

	/* Send QueryCancel if we are processing a database query */
	if (cancelConn != NULL)
	{
		if (PQcancel(cancelConn, errbuf, sizeof(errbuf)))
			fprintf(stderr, _("Cancel request sent\n"));
		else
			fprintf(stderr, _("Could not send cancel request: %s"), errbuf);
	}

	errno = save_errno;			/* just in case the write changed it */
}

/*
 * Handle interrupt signals by cancelling the current command.
 */
static void
on_interrupt(void)
{
	int			save_errno = errno;
	char		errbuf[256];

	/* Set interrupted flag */
	interrupted = true;

	/* Send QueryCancel if we are processing a database query */
	if (!in_cleanup && cancel_conn != NULL &&
		PQcancel(cancel_conn, errbuf, sizeof(errbuf)))
	{
		elog(WARNING, "cancel request was sent");
	}

	errno = save_errno;			/* just in case the write changed it */
}